drivers/staging/zram/zram_drv.c

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #define KMSG_COMPONENT "zram"
  16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  17
  18 #ifdef CONFIG_ZRAM_DEBUG
  19 #define DEBUG
  20 #endif
  21
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/bio.h>
  25 #include <linux/bitops.h>
  26 #include <linux/blkdev.h>
  27 #include <linux/buffer_head.h>
  28 #include <linux/device.h>
  29 #include <linux/genhd.h>
  30 #include <linux/highmem.h>
  31 #include <linux/slab.h>
  32 #include <linux/lzo.h>
  33 #include <linux/string.h>
  34 #include <linux/vmalloc.h>
  35
  36 #include "zram_drv.h"
  37
  38 /* Globals */
  39 static int zram_major;
  40 struct zram *zram_devices;
  41
  42 /* Module params (documentation at end) */
  43 static unsigned int num_devices = 1;
  44
  45 static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
  46 {
  47         spin_lock(&zram->stat64_lock);
  48         *v = *v + inc;
  49         spin_unlock(&zram->stat64_lock);
  50 }
  51
  52 static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
  53 {
  54         spin_lock(&zram->stat64_lock);
  55         *v = *v - dec;
  56         spin_unlock(&zram->stat64_lock);
  57 }
  58
  59 static void zram_stat64_inc(struct zram *zram, u64 *v)
  60 {
  61         zram_stat64_add(zram, v, 1);
  62 }
  63
  64 static int zram_test_flag(struct zram_meta *meta, u32 index,
  65                         enum zram_pageflags flag)
  66 {
  67         return meta->table[index].flags & BIT(flag);
  68 }
  69
  70 static void zram_set_flag(struct zram_meta *meta, u32 index,
  71                         enum zram_pageflags flag)
  72 {
  73         meta->table[index].flags |= BIT(flag);
  74 }
  75
  76 static void zram_clear_flag(struct zram_meta *meta, u32 index,
  77                         enum zram_pageflags flag)
  78 {
  79         meta->table[index].flags &= ~BIT(flag);
  80 }
  81
  82 static int page_zero_filled(void *ptr)
  83 {
  84         unsigned int pos;
  85         unsigned long *page;
  86
  87         page = (unsigned long *)ptr;
  88
  89         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
  90                 if (page[pos])
  91                         return 0;
  92         }
  93
  94         return 1;
  95 }
  96
  97 static void zram_free_page(struct zram *zram, size_t index)
  98 {
  99         struct zram_meta *meta = zram->meta;
 100         unsigned long handle = meta->table[index].handle;
 101         u16 size = meta->table[index].size;
 102
 103         if (unlikely(!handle)) {
 104                 /*
 105                  * No memory is allocated for zero filled pages.
 106                  * Simply clear zero page flag.
 107                  */
 108                 if (zram_test_flag(meta, index, ZRAM_ZERO)) {
 109                         zram_clear_flag(meta, index, ZRAM_ZERO);
 110                         zram->stats.pages_zero--;
 111                 }
 112                 return;
 113         }
 114
 115         if (unlikely(size > max_zpage_size))
 116                 zram->stats.bad_compress--;
 117
 118         zs_free(meta->mem_pool, handle);
 119
 120         if (size <= PAGE_SIZE / 2)
 121                 zram->stats.good_compress--;
 122
 123         zram_stat64_sub(zram, &zram->stats.compr_size,
 124                         meta->table[index].size);
 125         zram->stats.pages_stored--;
 126
 127         meta->table[index].handle = 0;
 128         meta->table[index].size = 0;
 129 }
 130
 131 static void handle_zero_page(struct bio_vec *bvec)
 132 {
 133         struct page *page = bvec->bv_page;
 134         void *user_mem;
 135
 136         user_mem = kmap_atomic(page);
 137         memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
 138         kunmap_atomic(user_mem);
 139
 140         flush_dcache_page(page);
 141 }
 142
 143 static inline int is_partial_io(struct bio_vec *bvec)
 144 {
 145         return bvec->bv_len != PAGE_SIZE;
 146 }
 147
 148 static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 149 {
 150         int ret = LZO_E_OK;
 151         size_t clen = PAGE_SIZE;
 152         unsigned char *cmem;
 153         struct zram_meta *meta = zram->meta;
 154         unsigned long handle = meta->table[index].handle;
 155
 156         if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
 157                 memset(mem, 0, PAGE_SIZE);
 158                 return 0;
 159         }
 160
 161         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 162         if (meta->table[index].size == PAGE_SIZE)
 163                 memcpy(mem, cmem, PAGE_SIZE);
 164         else
 165                 ret = lzo1x_decompress_safe(cmem, meta->table[index].size,
 166                                                 mem, &clen);
 167         zs_unmap_object(meta->mem_pool, handle);
 168
 169         /* Should NEVER happen. Return bio error if it does. */
 170         if (unlikely(ret != LZO_E_OK)) {
 171                 pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
 172                 zram_stat64_inc(zram, &zram->stats.failed_reads);
 173                 return ret;
 174         }
 175
 176         return 0;
 177 }
 178
 179 static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
 180                           u32 index, int offset, struct bio *bio)
 181 {
 182         int ret;
 183         struct page *page;
 184         unsigned char *user_mem, *uncmem = NULL;
 185         struct zram_meta *meta = zram->meta;
 186         page = bvec->bv_page;
 187
 188         if (unlikely(!meta->table[index].handle) ||
 189                         zram_test_flag(meta, index, ZRAM_ZERO)) {
 190                 handle_zero_page(bvec);
 191                 return 0;
 192         }
 193
 194         if (is_partial_io(bvec))
 195                 /* Use  a temporary buffer to decompress the page */
 196                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 197
 198         user_mem = kmap_atomic(page);
 199         if (!is_partial_io(bvec))
 200                 uncmem = user_mem;
 201
 202         if (!uncmem) {
 203                 pr_info("Unable to allocate temp memory\n");
 204                 ret = -ENOMEM;
 205                 goto out_cleanup;
 206         }
 207
 208         ret = zram_decompress_page(zram, uncmem, index);
 209         /* Should NEVER happen. Return bio error if it does. */
 210         if (unlikely(ret != LZO_E_OK))
 211                 goto out_cleanup;
 212
 213         if (is_partial_io(bvec))
 214                 memcpy(user_mem + bvec->bv_offset, uncmem + offset,
 215                                 bvec->bv_len);
 216
 217         flush_dcache_page(page);
 218         ret = 0;
 219 out_cleanup:
 220         kunmap_atomic(user_mem);
 221         if (is_partial_io(bvec))
 222                 kfree(uncmem);
 223         return ret;
 224 }
 225
 226 static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 227                            int offset)
 228 {
 229         int ret = 0;
 230         size_t clen;
 231         unsigned long handle;
 232         struct page *page;
 233         unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
 234         struct zram_meta *meta = zram->meta;
 235
 236         page = bvec->bv_page;
 237         src = meta->compress_buffer;
 238
 239         if (is_partial_io(bvec)) {
 240                 /*
 241                  * This is a partial IO. We need to read the full page
 242                  * before to write the changes.
 243                  */
 244                 uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
 245                 if (!uncmem) {
 246                         ret = -ENOMEM;
 247                         goto out;
 248                 }
 249                 ret = zram_decompress_page(zram, uncmem, index);
 250                 if (ret)
 251                         goto out;
 252         }
 253
 254         /*
 255          * System overwrites unused sectors. Free memory associated
 256          * with this sector now.
 257          */
 258         if (meta->table[index].handle ||
 259             zram_test_flag(meta, index, ZRAM_ZERO))
 260                 zram_free_page(zram, index);
 261
 262         user_mem = kmap_atomic(page);
 263
 264         if (is_partial_io(bvec)) {
 265                 memcpy(uncmem + offset, user_mem + bvec->bv_offset,
 266                        bvec->bv_len);
 267                 kunmap_atomic(user_mem);
 268                 user_mem = NULL;
 269         } else {
 270                 uncmem = user_mem;
 271         }
 272
 273         if (page_zero_filled(uncmem)) {
 274                 kunmap_atomic(user_mem);
 275                 zram->stats.pages_zero++;
 276                 zram_set_flag(meta, index, ZRAM_ZERO);
 277                 ret = 0;
 278                 goto out;
 279         }
 280
 281         ret = lzo1x_1_compress(uncmem, PAGE_SIZE, src, &clen,
 282                                meta->compress_workmem);
 283
 284         if (!is_partial_io(bvec)) {
 285                 kunmap_atomic(user_mem);
 286                 user_mem = NULL;
 287                 uncmem = NULL;
 288         }
 289
 290         if (unlikely(ret != LZO_E_OK)) {
 291                 pr_err("Compression failed! err=%d\n", ret);
 292                 goto out;
 293         }
 294
 295         if (unlikely(clen > max_zpage_size)) {
 296                 zram->stats.bad_compress++;
 297                 clen = PAGE_SIZE;
 298                 src = NULL;
 299                 if (is_partial_io(bvec))
 300                         src = uncmem;
 301         }
 302
 303         handle = zs_malloc(meta->mem_pool, clen);
 304         if (!handle) {
 305                 pr_info("Error allocating memory for compressed "
 306                         "page: %u, size=%zu\n", index, clen);
 307                 ret = -ENOMEM;
 308                 goto out;
 309         }
 310         cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
 311
 312         if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
 313                 src = kmap_atomic(page);
 314         memcpy(cmem, src, clen);
 315         if ((clen == PAGE_SIZE) && !is_partial_io(bvec))
 316                 kunmap_atomic(src);
 317
 318         zs_unmap_object(meta->mem_pool, handle);
 319
 320         meta->table[index].handle = handle;
 321         meta->table[index].size = clen;
 322
 323         /* Update stats */
 324         zram_stat64_add(zram, &zram->stats.compr_size, clen);
 325         zram->stats.pages_stored++;
 326         if (clen <= PAGE_SIZE / 2)
 327                 zram->stats.good_compress++;
 328
 329 out:
 330         if (is_partial_io(bvec))
 331                 kfree(uncmem);
 332
 333         if (ret)
 334                 zram_stat64_inc(zram, &zram->stats.failed_writes);
 335         return ret;
 336 }
 337
 338 static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
 339                         int offset, struct bio *bio, int rw)
 340 {
 341         int ret;
 342
 343         if (rw == READ) {
 344                 down_read(&zram->lock);
 345                 ret = zram_bvec_read(zram, bvec, index, offset, bio);
 346                 up_read(&zram->lock);
 347         } else {
 348                 down_write(&zram->lock);
 349                 ret = zram_bvec_write(zram, bvec, index, offset);
 350                 up_write(&zram->lock);
 351         }
 352
 353         return ret;
 354 }
 355
 356 static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
 357 {
 358         if (*offset + bvec->bv_len >= PAGE_SIZE)
 359                 (*index)++;
 360         *offset = (*offset + bvec->bv_len) % PAGE_SIZE;
 361 }
 362
 363 static void __zram_make_request(struct zram *zram, struct bio *bio, int rw)
 364 {
 365         int i, offset;
 366         u32 index;
 367         struct bio_vec *bvec;
 368
 369         switch (rw) {
 370         case READ:
 371                 zram_stat64_inc(zram, &zram->stats.num_reads);
 372                 break;
 373         case WRITE:
 374                 zram_stat64_inc(zram, &zram->stats.num_writes);
 375                 break;
 376         }
 377
 378         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 379         offset = (bio->bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
 380
 381         bio_for_each_segment(bvec, bio, i) {
 382                 int max_transfer_size = PAGE_SIZE - offset;
 383
 384                 if (bvec->bv_len > max_transfer_size) {
 385                         /*
 386                          * zram_bvec_rw() can only make operation on a single
 387                          * zram page. Split the bio vector.
 388                          */
 389                         struct bio_vec bv;
 390
 391                         bv.bv_page = bvec->bv_page;
 392                         bv.bv_len = max_transfer_size;
 393                         bv.bv_offset = bvec->bv_offset;
 394
 395                         if (zram_bvec_rw(zram, &bv, index, offset, bio, rw) < 0)
 396                                 goto out;
 397
 398                         bv.bv_len = bvec->bv_len - max_transfer_size;
 399                         bv.bv_offset += max_transfer_size;
 400                         if (zram_bvec_rw(zram, &bv, index+1, 0, bio, rw) < 0)
 401                                 goto out;
 402                 } else
 403                         if (zram_bvec_rw(zram, bvec, index, offset, bio, rw)
 404                             < 0)
 405                                 goto out;
 406
 407                 update_position(&index, &offset, bvec);
 408         }
 409
 410         set_bit(BIO_UPTODATE, &bio->bi_flags);
 411         bio_endio(bio, 0);
 412         return;
 413
 414 out:
 415         bio_io_error(bio);
 416 }
 417
 418 /*
 419  * Check if request is within bounds and aligned on zram logical blocks.
 420  */
 421 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 422 {
 423         if (unlikely(
 424                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 425                 (bio->bi_sector & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)) ||
 426                 (bio->bi_size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))) {
 427
 428                 return 0;
 429         }
 430
 431         /* I/O request is valid */
 432         return 1;
 433 }
 434
 435 /*
 436  * Handler function for all zram I/O requests.
 437  */
 438 static void zram_make_request(struct request_queue *queue, struct bio *bio)
 439 {
 440         struct zram *zram = queue->queuedata;
 441
 442         down_read(&zram->init_lock);
 443         if (unlikely(!zram->init_done))
 444                 goto error;
 445
 446         if (!valid_io_request(zram, bio)) {
 447                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 448                 goto error;
 449         }
 450
 451         __zram_make_request(zram, bio, bio_data_dir(bio));
 452         up_read(&zram->init_lock);
 453
 454         return;
 455
 456 error:
 457         up_read(&zram->init_lock);
 458         bio_io_error(bio);
 459 }
 460
 461 static void __zram_reset_device(struct zram *zram)
 462 {
 463         size_t index;
 464         struct zram_meta *meta;
 465
 466         if (!zram->init_done)
 467                 return;
 468
 469         meta = zram->meta;
 470         zram->init_done = 0;
 471
 472         /* Free all pages that are still in this zram device */
 473         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 474                 unsigned long handle = meta->table[index].handle;
 475                 if (!handle)
 476                         continue;
 477
 478                 zs_free(meta->mem_pool, handle);
 479         }
 480
 481         zram_meta_free(zram->meta);
 482         zram->meta = NULL;
 483         /* Reset stats */
 484         memset(&zram->stats, 0, sizeof(zram->stats));
 485
 486         zram->disksize = 0;
 487         set_capacity(zram->disk, 0);
 488 }
 489
 490 void zram_reset_device(struct zram *zram)
 491 {
 492         down_write(&zram->init_lock);
 493         __zram_reset_device(zram);
 494         up_write(&zram->init_lock);
 495 }
 496
 497 void zram_meta_free(struct zram_meta *meta)
 498 {
 499         zs_destroy_pool(meta->mem_pool);
 500         kfree(meta->compress_workmem);
 501         free_pages((unsigned long)meta->compress_buffer, 1);
 502         vfree(meta->table);
 503         kfree(meta);
 504 }
 505
 506 struct zram_meta *zram_meta_alloc(u64 disksize)
 507 {
 508         size_t num_pages;
 509         struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
 510         if (!meta)
 511                 goto out;
 512
 513         meta->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 514         if (!meta->compress_workmem)
 515                 goto free_meta;
 516
 517         meta->compress_buffer =
 518                 (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
 519         if (!meta->compress_buffer) {
 520                 pr_err("Error allocating compressor buffer space\n");
 521                 goto free_workmem;
 522         }
 523
 524         num_pages = disksize >> PAGE_SHIFT;
 525         meta->table = vzalloc(num_pages * sizeof(*meta->table));
 526         if (!meta->table) {
 527                 pr_err("Error allocating zram address table\n");
 528                 goto free_buffer;
 529         }
 530
 531         meta->mem_pool = zs_create_pool(GFP_NOIO | __GFP_HIGHMEM);
 532         if (!meta->mem_pool) {
 533                 pr_err("Error creating memory pool\n");
 534                 goto free_table;
 535         }
 536
 537         return meta;
 538
 539 free_table:
 540         vfree(meta->table);
 541 free_buffer:
 542         free_pages((unsigned long)meta->compress_buffer, 1);
 543 free_workmem:
 544         kfree(meta->compress_workmem);
 545 free_meta:
 546         kfree(meta);
 547         meta = NULL;
 548 out:
 549         return meta;
 550 }
 551
 552 void zram_init_device(struct zram *zram, struct zram_meta *meta)
 553 {
 554         if (zram->disksize > 2 * (totalram_pages << PAGE_SHIFT)) {
 555                 pr_info(
 556                 "There is little point creating a zram of greater than "
 557                 "twice the size of memory since we expect a 2:1 compression "
 558                 "ratio. Note that zram uses about 0.1%% of the size of "
 559                 "the disk when not in use so a huge zram is "
 560                 "wasteful.\n"
 561                 "\tMemory Size: %lu kB\n"
 562                 "\tSize you selected: %llu kB\n"
 563                 "Continuing anyway ...\n",
 564                 (totalram_pages << PAGE_SHIFT) >> 10, zram->disksize >> 10
 565                 );
 566         }
 567
 568         /* zram devices sort of resembles non-rotational disks */
 569         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 570
 571         zram->meta = meta;
 572         zram->init_done = 1;
 573
 574         pr_debug("Initialization done!\n");
 575 }
 576
 577 static void zram_slot_free_notify(struct block_device *bdev,
 578                                 unsigned long index)
 579 {
 580         struct zram *zram;
 581
 582         zram = bdev->bd_disk->private_data;
 583         down_write(&zram->lock);
 584         zram_free_page(zram, index);
 585         up_write(&zram->lock);
 586         zram_stat64_inc(zram, &zram->stats.notify_free);
 587 }
 588
 589 static const struct block_device_operations zram_devops = {
 590         .swap_slot_free_notify = zram_slot_free_notify,
 591         .owner = THIS_MODULE
 592 };
 593
 594 static int create_device(struct zram *zram, int device_id)
 595 {
 596         int ret = -ENOMEM;
 597
 598         init_rwsem(&zram->lock);
 599         init_rwsem(&zram->init_lock);
 600         spin_lock_init(&zram->stat64_lock);
 601
 602         zram->queue = blk_alloc_queue(GFP_KERNEL);
 603         if (!zram->queue) {
 604                 pr_err("Error allocating disk queue for device %d\n",
 605                         device_id);
 606                 goto out;
 607         }
 608
 609         blk_queue_make_request(zram->queue, zram_make_request);
 610         zram->queue->queuedata = zram;
 611
 612          /* gendisk structure */
 613         zram->disk = alloc_disk(1);
 614         if (!zram->disk) {
 615                 pr_warn("Error allocating disk structure for device %d\n",
 616                         device_id);
 617                 goto out_free_queue;
 618         }
 619
 620         zram->disk->major = zram_major;
 621         zram->disk->first_minor = device_id;
 622         zram->disk->fops = &zram_devops;
 623         zram->disk->queue = zram->queue;
 624         zram->disk->private_data = zram;
 625         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 626
 627         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 628         set_capacity(zram->disk, 0);
 629
 630         /*
 631          * To ensure that we always get PAGE_SIZE aligned
 632          * and n*PAGE_SIZED sized I/O requests.
 633          */
 634         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 635         blk_queue_logical_block_size(zram->disk->queue,
 636                                         ZRAM_LOGICAL_BLOCK_SIZE);
 637         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 638         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 639
 640         add_disk(zram->disk);
 641
 642         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 643                                 &zram_disk_attr_group);
 644         if (ret < 0) {
 645                 pr_warn("Error creating sysfs group");
 646                 goto out_free_disk;
 647         }
 648
 649         zram->init_done = 0;
 650         return 0;
 651
 652 out_free_disk:
 653         del_gendisk(zram->disk);
 654         put_disk(zram->disk);
 655 out_free_queue:
 656         blk_cleanup_queue(zram->queue);
 657 out:
 658         return ret;
 659 }
 660
 661 static void destroy_device(struct zram *zram)
 662 {
 663         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 664                         &zram_disk_attr_group);
 665
 666         if (zram->disk) {
 667                 del_gendisk(zram->disk);
 668                 put_disk(zram->disk);
 669         }
 670
 671         if (zram->queue)
 672                 blk_cleanup_queue(zram->queue);
 673 }
 674
 675 unsigned int zram_get_num_devices(void)
 676 {
 677         return num_devices;
 678 }
 679
 680 static int __init zram_init(void)
 681 {
 682         int ret, dev_id;
 683
 684         if (num_devices > max_num_devices) {
 685                 pr_warn("Invalid value for num_devices: %u\n",
 686                                 num_devices);
 687                 ret = -EINVAL;
 688                 goto out;
 689         }
 690
 691         zram_major = register_blkdev(0, "zram");
 692         if (zram_major <= 0) {
 693                 pr_warn("Unable to get major number\n");
 694                 ret = -EBUSY;
 695                 goto out;
 696         }
 697
 698         /* Allocate the device array and initialize each one */
 699         zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 700         if (!zram_devices) {
 701                 ret = -ENOMEM;
 702                 goto unregister;
 703         }
 704
 705         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 706                 ret = create_device(&zram_devices[dev_id], dev_id);
 707                 if (ret)
 708                         goto free_devices;
 709         }
 710
 711         pr_info("Created %u device(s) ...\n", num_devices);
 712
 713         return 0;
 714
 715 free_devices:
 716         while (dev_id)
 717                 destroy_device(&zram_devices[--dev_id]);
 718         kfree(zram_devices);
 719 unregister:
 720         unregister_blkdev(zram_major, "zram");
 721 out:
 722         return ret;
 723 }
 724
 725 static void __exit zram_exit(void)
 726 {
 727         int i;
 728         struct zram *zram;
 729
 730         for (i = 0; i < num_devices; i++) {
 731                 zram = &zram_devices[i];
 732
 733                 get_disk(zram->disk);
 734                 destroy_device(zram);
 735                 zram_reset_device(zram);
 736                 put_disk(zram->disk);
 737         }
 738
 739         unregister_blkdev(zram_major, "zram");
 740
 741         kfree(zram_devices);
 742         pr_debug("Cleanup done!\n");
 743 }
 744
 745 module_param(num_devices, uint, 0);
 746 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 747
 748 module_init(zram_init);
 749 module_exit(zram_exit);
 750
 751 MODULE_LICENSE("Dual BSD/GPL");
 752 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 753 MODULE_DESCRIPTION("Compressed RAM Block Device");